1. Field of the Invention
The present invention relates to a tuning fork vibrator for use in a device for correcting an error caused by hand movements or vibrations that occur during operation of a video camera, for example, a vibrating gyroscope including the vibrator, an electronic apparatus including the vibrator, and a method of manufacturing the tuning fork vibrator.
2. Description of the Related Art
Examples of conventional tuning fork vibrators are disclosed in Patent Document 1 (referred to below as Conventional Example 1) and Patent Document 2 (referred to below as Conventional Example 2).
In the tuning fork vibrator of the Conventional Example 1, as shown in FIG. 22, a tuning fork vibrator 1 includes a long plate-shaped piezoelectric member 2, in which a slit 3 is formed to extend from the first principal surface thereof to the second principal surface by cutting the piezoelectric member 2 from one end thereof so as to form two legs 4 and 5.
A tuning fork vibrator in the Conventional Example 2, as shown in FIG. 1 of Patent Document 2, includes two piezoelectric columnar vibrators arranged such that an end of each of the vibrators is fixed to a base.
The description of driving methods of conventional tuning fork vibrators is omitted.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 8-128830
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2000-193458
It is difficult to manufacture the tuning fork vibrator according to the Conventional Example 1 by cutting a piezoelectric member from the first principal surface or the second principal surface using a dicing saw to form a slit between two legs. As shown in FIG. 23, a block 6 is made by bonding a plurality of piezoelectric members prior to forming slits in the thickness direction and the width direction, slits 3 are formed on the block 6 using a wire saw or a dicing saw, and the piezoelectric members 2 that are bonded together are separated.
However, this method complicates the manufacturing process by requiring initial bonding of the piezoelectric members which must be followed by the step of separating them. If an electrode is formed on the first principal surface or the second principal surface of the tuning fork vibrator, the electrode must be formed for each separated tuning fork vibrator, which further complicates the manufacturing process. If the electrodes are formed on a mother substrate prior to forming slits, the electrode-forming process must be performed prior to the slit-forming process, such that the positional accuracy of the electrodes on a leg portion deteriorates.
On the other hand, since in the tuning fork vibrator according to the Conventional Example 2, each vibrator is columnar-shaped, each vibrator is easily separated from a mother substrate using a dicing saw. Electrodes formed in advance on a front surface of the mother substrate, on which grooves are made by a dicing saw, can be separated prior to separating each vibrator with the same dicing saw. Since the separation of the electrodes and the separation of the vibrators are performed in a single process, the problems of Conventional Example 1 are eliminated.
However, in the Conventional Example 2, because the vibrator is not integral with a base, the number of parts increases which complicates the manufacturing process. In addition, when two vibrators are fixed to one base, positional displacement and unbalanced fixing strength make it difficult to achieve a well-balanced tuning fork vibrator.
In order to overcome the problems described above, preferred embodiments of the present invention provide a well-balanced tuning fork vibrator, a vibrating gyroscope including the tuning fork vibrator, an electronic apparatus including the tuning fork vibrator, and a method of manufacturing the tuning fork vibrator.
A tuning fork vibrator according to a preferred embodiment of the present invention includes a long plate-shaped vibration unit having a first principal surface and a second principal surface, a base disposed at one end of the second principal surface of the vibration unit in the longitudinal direction, wherein at least one slit for dividing the vibration unit into at least two legs along the longitudinal direction symmetrically in the width direction of the vibration unit is provided in the vibration unit, and the slit includes a portion of the base that is in the vicinity of the vibration unit.
In the tuning fork vibrator, the vibration unit is preferably divided into at least three legs by the slits, and further includes a support pin fixed to the leg in the vicinity of the center of the second principal surface. The support pin supports the vibration unit and the base in midair.
The base preferably has a substantially U-shaped configuration including three straight line-segments which surround the vibration unit on three sides, which are provided on one end side in the longitudinal direction and on both sides in the width direction. Alternatively, the base may have a substantially rectangular frame-shape which surrounds the vibration unit on four sides.
In the tuning fork vibrator according to preferred embodiments of the present invention, the base is preferably integrated at least with the second principal surface of the vibration unit. Alternatively, the base may be provided separately from the vibration unit, and bonded to the vibration unit.
Furthermore, the vibration unit may have a bimorph structure including bonded piezoelectric members which are polarized in opposite directions to each other in a direction of the thickness between the first principal surface and the second principal surface of the vibration unit, a unimorph structure including a piezoelectric member polarized in the thickness direction and a non-piezoelectric material which are bonded together, or a structure including a non-piezoelectric material, in which a piezoelectric element which is polarized in the thickness direction of the vibration unit is provided on one principal surface of the non-piezoelectric material.
A vibrating gyroscope according to another preferred embodiment of the present invention includes the tuning fork vibrator described above.
A vibrating gyroscope according to various preferred embodiments of the present invention includes a tuning fork vibrator having two long legs formed by bonding piezoelectric members polarized in opposite directions to each other in a direction of the thickness between a first principal surface and a second principal surface, so as to have a tuning fork shape with one end thereof fixed, wherein two electrodes divided in the width direction are provided on the first principal surface of the respective two legs while an electrode is provided on the second principal surface, wherein among the four electrodes provided on the first principal surface of the respective two legs, two electrodes arranged inside-to-inside or outside-to-outside are connected together to define a driving electrode and the remaining two electrodes define a detection electrode which also defines as a feedback electrode, and the electrodes provided on the second principal surfaces of the two legs are further connected together and are connected to a reference voltage or are floating. This tuning fork vibrator preferably has a bimorph structure described above.
Also, a vibrating gyroscope according to preferred embodiments of the present invention includes a tuning fork vibrator having two long legs formed by bonding a piezoelectric member, being polarized in the thickness direction and having two electrodes divided in the width direction on a first principal surface and an electrode on a second principal surface, to a non-piezoelectric element, so as to have the first principal surface and the second principal surface, respectively, and arranged in a tuning fork shape with one end thereof fixed, wherein among the four electrodes provided on the first principal surface of the respective two legs, two electrodes which are disposed inside-to-inside or outside-to-outside are connected together to define a driving electrode and the remaining two electrodes define a detection electrode which also defines a feedback electrode, and wherein the electrodes provided on the second principal surfaces of the two legs are connected together while being connected to a reference voltage or are floating. This tuning fork vibrator preferably has the unimorph structure described above.
A vibrating gyroscope according to preferred embodiments of the present invention includes a tuning fork vibrator having two long legs which are made of a non-piezoelectric material and is arranged in a tuning fork shape with one end thereof being fixed, wherein piezoelectric elements are polarized in a thickness direction and provided on a first principal surface of the respective two legs, each of the piezoelectric elements including a lower electrode, a piezoelectric layer provided on the lower electrode, and two upper electrodes provided on the piezoelectric layer and divided in the width direction of the legs, and wherein among the four, upper electrodes, two electrodes which are disposed inside-to-inside or outside-to-outside are connected together to define a driving electrode and the remaining two electrodes define a detection electrode and also define a feedback electrode, and the entire lower electrodes are connected together while being connected to a reference voltage or are floating. This tuning fork vibrator preferably has a vibration unit which is made of the non-piezoelectric material.
An electronic apparatus according to another preferred embodiment of the present invention includes the vibrating gyroscope described above.
A method of manufacturing a tuning fork vibrator according to another preferred embodiment of the present invention includes the steps of forming at least one long deletion portion having a predetermined length, width, and depth and at least one long non-deletion portion arranged adjacent to the deletion portion in the width direction thereof by scraping a second principal surface of a mother substrate having a first principal surface and a second principal surface, forming a first slit for completely dividing the deletion portion along width directions of the deletion portion and the non-deletion portion from the first principal surface of the mother substrate, and forming second slits for cutting the mother substrate, one slit of the second slits extending in the width direction and another slit of the second slits extending in the longitudinal direction, in the deletion portion and the non-deletion portion, so as to define a block having a substantially rectangular shape in plan view which is longer in the width direction of the deletion portion and the non-deletion portion and having one piece of the deletion portion and one piece of the non-deletion portion, wherein the first slit is provided in the longitudinal direction of the block such that the block is symmetrical in the width direction thereof.
In addition, a method of manufacturing a tuning fork vibrator according to another preferred embodiment of the present invention includes the steps of forming at least one first slit substantially in parallel on a mother substrate having a first principal surface and a second principal surface from the first principal surface of the mother substrate, the first slit having a first depth that is less than the thickness of the mother substrate, forming second slits on the mother substrate from the first principal surface thereof, one of the second slits extending in the longitudinal direction of the first slit, and another of the second slits extending in a direction that is substantially perpendicular thereto, such that at least one first slit is included within a substantially rectangular area in a plan view formed in the mother substrate along the longitudinal direction of the area, the substantially rectangular area being longer in the longitudinal direction of the first slit, the second slit having a second depth that is less than the thickness of the mother substrate and greater than the first depth, forming a deletion portion in the second principal surface of the mother substrate by cutting the mother substrate at a position corresponding to one end in the longitudinal direction of a portion of the substantially rectangular area in plan view formed by the second slits until the first slit is completely exposed, and deleting a portion of the mother substrate having no deletion portion formed thereon from the first principal surface of the mother substrate until the second slits are completely exposed, wherein the first slit is provided in the longitudinal direction of the portion of the substantially rectangular area in plan view such that the portion is symmetrical in the width direction thereof.
Furthermore, a method of manufacturing a tuning fork vibrator according to another preferred embodiment of the present invention includes the steps of bonding at least one long plate-shaped base member on one of a first principal surface and a second principal surface of a mother substrate, the base member having a predetermined length, width, and thickness, forming a first slit for completely dividing the mother substrate from the first principal surface of the mother substrate along the width direction of the base member, and forming second slits for cutting the mother substrate and the base member in the base member, one second slit extending in the width direction and another second slit extending in the longitudinal direction, so as to have a block with a substantially rectangular shape in plan view which is longer in the width direction of the base member that in the longitudinal direction, the block with the substantially rectangular shape having one portion in only the base member and one portion in a portion of the mother substrate to which the base member is bonded, wherein the first slit extends in the longitudinal direction of the block such that the block is symmetrical about the first slit in the width direction thereof.
A method of manufacturing a tuning fork vibrator according to another preferred embodiment of the present invention includes the steps of bonding one principal surface of a base mother substrate having a recess or a through-hole with a substantially rectangular shape in plan view formed therein on one of a first principal surface and a second principal surface of a mother substrate from the first principal surface of the mother substrate, forming a first slit for completely dividing the mother substrate in the first principal surface of the mother substrate, and forming a second slit for completely dividing the mother substrate and the base mother substrate, wherein the first slit includes at least three slits, which are arranged along the longitudinal direction of the recess or the through-hole substantially in parallel with each other and pass through the recess or the through-hole in plan view, and wherein the second slit includes slits, which are arranged in longitudinal and width directions of the recess or the through-hole such that the recess or the through-hole is completely included within a substantially rectangular area formed by the second slits, and a slit for completely dividing the recess or the through-hole of the base mother substrate in two along the longitudinal direction.
Furthermore, a method of manufacturing a tuning fork vibrator according to another preferred embodiment of the present invention includes the steps of bonding one principal surface of a base mother substrate having a recess or a through-hole with a substantially rectangular shape in plan view formed therein on one of a first principal surface and a second principal surface of a mother substrate from the first principal surface of the mother substrate, forming a first slit for completely dividing the mother substrate in the first principal surface of the mother substrate, and forming a second slit for completely dividing the mother substrate and the base mother substrate, wherein the first slit includes at least three slits arranged along the longitudinal direction of the recess or the through-hole substantially in parallel to each other and passing through the recess or the through-hole and one slit arranged along the width direction of the recess or the through-hole, and wherein the second slit includes slits that are arranged in directions of the recess or the through-hole, one second slit along the longitudinal direction, another second slit along the width direction, such that the recess or the through-hole is completely included within a substantially rectangular area formed by the second slits.
Furthermore, a method of manufacturing a tuning fork vibrator according to another preferred embodiment the present invention includes the steps of forming a substantially rectangular recess having a predetermined depth in one of a first principal surface and a second principal surface of a mother substrate, forming a first slit in the first principal surface of the mother substrate, the depth of the first slit being greater than the length obtained by subtracting the predetermined depth of the recess from the thickness of the mother substrate, and forming a second slit for completely dividing the mother substrate, wherein the first slit includes at least three slits, which are arranged along the longitudinal direction of the recess substantially in parallel with each other and pass through within the recess in plan view, and wherein the second slit includes slits, which are arranged in directions of the recess, one second slit along the longitudinal direction, another second slit along the width direction, such that the recess is completely included within a substantially rectangular area formed by the second slits, and a slit for completely dividing the recess into two along the longitudinal direction.
Furthermore, a method of manufacturing a tuning fork vibrator according to another preferred embodiment of the present invention includes the steps of forming a substantially rectangular recess having a predetermined depth in one of first and second principal surfaces of a mother substrate, forming a first slit in the first principal surface of the mother substrate, the depth of the first slit being greater than the length obtained by subtracting the predetermined depth of the recess from the thickness of the mother substrate, and forming a second slit for completely dividing the mother substrate, wherein the first slit includes at least three slits arranged along the longitudinal direction of the recess substantially in parallel to each other and passing through the recess and one slit arranged along the width direction of the recess and passing through the recess, and wherein the second slit includes slits arranged such that the recess is completely included within a substantially rectangular area formed by the second slits.
With the methods described above, the manufacturing process is greatly simplified. Also, in the tuning fork vibrator, the precision of the size of electrodes formed on the legs and the bottom is greatly increased and the balance of the two legs with the base is greatly improved. Moreover, the dispersion in characteristics between a plurality of tuning fork vibrators is also reduced.
In the vibrating gyroscope according to preferred embodiments of the present invention, an angular velocity is detected with high precision.
In the electronic apparatus according to preferred embodiments of the present invention, since the vibrating gyroscope according to preferred embodiments of the present invention is provided, precise angular velocity information is consistently obtained, such that the performance of the electronic apparatus is greatly improved.
Other features, elements, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments thereof with reference to the attached drawings.